A light emitting diode comprises a multiple quantum well structure. The light emitting diode has a first conductivity type GaAs substrate, an AlGaInP lower cladding layer of the first conductivity type, a multiple quantum well structure, an AlGaInP upper cladding layer of a second conductivity type, and a window structure of the second conductivity type. The multiple quantum well structure comprises a plurality of AlGaInP quantum well layers and barrier layers being stacked alternatively on each other. The window structure including a thin layer having low energy band gap and high conductivity GaAs or GaInP, and a thicker layer having high energy band gap and transparent GaP containing a small amount of In. The use of multiple quantum well structure improves the light intensity and the Iv-I curve linearity of the light emitting diode. The small amount of In in the window layer reduces the defect density generated in the GaP layer due to the lattice mismatch between the window layer and the upper cladding layer. Another improvement that includes growing a distributed Bragg reflector layer between the lower cladding layer and substrate is also presented to further increase the luminous efficiency of the light emitting diode.